The genome contains the information of life. It is the biological code that serves both as a historical record of our past – who our relatives are – and as a guide to our future growth and development. This code is found in the nucleus of each of the three trillion cells in the human body: genomes are organized into 23 chromosome pairs, and within each of those chromosomes, the basic unit of genetic information, called DNA (or deoxyribonucleic acid), is strung along in a double-helix structure. What’s encoded in our genome informs everything from our hair colour to whether we are likely to get cancer: Some DNA is grouped into genes that encode these characteristics directly, other parts of the genome control genes themselves, turning them on or off. Lifestyle and environmental factors can also influence the expression of genes.

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Swiss biochemist Friedrich Miescher was the first to identify DNA as a distinct molecule while working in Germany in 1869. But nobody knew what this molecule was until more than eight decades later. It was the discovery in 1953 of the double-helix structure of DNA that revealed its importance – that it contained the basic information of life, which could in turn be unzipped, duplicated and passed on to future generations.

The iconic double helix was proposed by two molecular biologists, American James Watson and England’s Francis Crick, at the University of Cambridge. Rosalind Franklin and Maurice Wilkins then provided independent evidence to support their ingenious DNA structure. In 1962, Watson, Crick and Wilkins all won the Nobel Prize in physiology or medicine for their groundbreaking research (Franklin died in 1958).

In 1990, the research by this Nobel team was pushed further with the Human Genome Project, created by the U.S. Department of Energy and the National Institutes of Health to determine the order of our three billion DNA base pairs (since there are two strands in the DNA helix, there are a total of six billion base pairs) and the 20,000 genes that provide what we now think of as “instructions” for life. A first draft of the genome was announced in 2000 and the complete map was finished in 2003.

What your genes can tell you

While genetic science is still in its infancy, there are already private companies who will share what we know so far – for a price. For example, at 23andMe, a company in Mountain View, Calif., $299 and a bit of your spit buy you the chance to have your DNA analyzed. Customers can trace their recent ancestry by comparing genomes with 150,000 other members, or go back into deep history and find out whether they carry traces of Neanderthal genes. They can also investigate their susceptibility to health risks; tests check for more than 40 inherited diseases, including cystic fibrosis and sickle cell anemia. While there are a number of such genetic testing companies in the U.S., Canada has been slower to catch on. That is changing, however, as examples like the DNA Testing Centres of Canada headquartered in Oakville, Ont., suggests.